1. Field of the Invention
The present invention relates to light microscopes including light microscopes having dual eyepiece (binocular) viewing and the ability to produce a stereoscopic (stereo) image that can be viewed and/or photographed in real time. The invention further relates to reflected light illumination (including epi illuminated fluorescent images) for microscopes with reduced flare without reduced specimen illumination.
2. The Prior Art
Although many microscopes are equipped with a binocular viewing arrangement, that alone does not produce a stereoscopic view of an object since both of the viewing eyepieces typically see the exact same image from the same angle. Stereoscopic viewing requires that each eye see a different image of the object. This is accomplished by creating parallax (viewing the object from different angles) in much the same way that human eye pairs create stereoscopic vision.
At the present time there are two types of stereoscopic microscopes widely known and used. The first of these (inclined axes type) is, in essence, two complete microscopes with their objectives close together and with their major axes inclined to each other to permit object viewing from two different angles to create the parallax necessary for producing a stereo pair. An example of this type of microscope is the Nikon.RTM. model SMZ-2B/2T.
The other type of stereo microscope (parallel-axis type) utilizes a single large objective lens followed by two smaller side-by-side lens groups whose axes are parallel to the objective lens axis and which share the aperture of the large objective. In this arrangement, only a small portion of the aperture of the large objective lens is used. An example of this type of microscope is the Nikon.RTM. model SMZ-10.
Both of these types of stereo microscopes have the well recognized limitation in the magnification that can be achieved. This limitation, that prevents total magnification of more than 100 times (approximately), is imposed by the practicalities of size and space. As magnification increases, the size of the objective (and its focal length and working distance) decreases. In the case of the inclined type of microscope, there is insufficient space for two objective lenses when the objective magnification exceeds approximately 10 times (the centers of the lenses need to be closer together than their physical size--radii--permits). Likewise, for the parallel-axis microscope, it is not possible to physically dispose two side-by-side secondary lenses behind the primary objective when the objective is diminished beyond a certain size (i.e. as the objective magnification increases beyond 10 times--approximately).
One undesirable characteristic of reflection illumination, and especially fluorescent illumination (either by virtue of natural fluorescence or the use of fluorescent markers), is flare, which if not controlled, can prevent good images from being captured. Prior art systems using epi fluorescent illumination, for example, have attempted to control flare by the use of an iris within the rear aperture of the objective. Since all such irises are optically disposed between the light source and the objective, they necessarily reduce the light that reaches the specimen as they reduce flare. Thus, the cost of controlling the flare is a reduction in the amount of light that reaches the specimen (object) and a concomitant reduction in the numerical aperture of illumination. While the control of flare in this way eliminates one source of image degradation, the accompanying light loss can prevent images from being recorded on film in some specimens and seriously reduces the quality of images that are achieved in others.